Explore the main circle theorems, and use the calculator modes where a numeric answer is meaningful.
The angle subtended by an arc at the center is twice the angle subtended at the circumference.
Enter a valid numeric angle in degrees.
Center angle
60°
Multiply the circumference angle by 2.
Circle theorems are geometric rules that describe relationships between angles, arcs, chords, and tangents within a circle.
They let you work out unknown angles without direct measurement.
A line segment with both endpoints on the circle.
A line that touches the circle at exactly one point.
A portion of the circumference between two points.
The region bounded by a chord and its arc.
Find the center angle when the circumference angle is 35°.
Given: 35°
Rule: Center angle = 2 × circumference angle
Answer: 70°
Result
70°
A four-sided shape whose vertices all lie on one circle.
No. Some theorems are descriptive and do not produce a numeric output.
Because the center angle subtends the same arc but spans twice the angle.
Yes. The calculator accepts numeric values, including decimals.
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